This invention relates generally to a semiconductor apparatus bonding method and, in particular, to a method of connecting multiple inner leads on tape carrier film to the electrodes of semiconductor elements.
Semiconductor apparatus of the tape carrier (TAB) type form multiple leads for each frame of tape comprising polyimide film or polyester film, join the respective electrodes of a semiconductor element to the tip portions of these leads, i.e. to the inner leads, cutting the tape, and mounting the assembly onto a printed substrate. Such substrates are capable of miniaturization and suitable for high density mounting.
Referring to FIGS. 6 and 7, bonding head 11 is supported so as to be vertically movable on apparatus main member 10. Head 11 may be driven up and down, for example, by a cam and is furnished with bonding tool 12 having a heater within a bonding head constructed so as to be capable of pressing down when driven by an air cylinder. Position recognition apparatus 13 is attached to bonding head 11. Guide plate 14 defines a hole 15 and is attached to bonding head 11. Guide rollers 16, 16a are mounted so as to be rotational on apparatus main member 10 and to direct carrier film along guide plate 14. The film has a length of, for example, 300 m and includes device holes 2 provided at prescribed intervals with multiple leads 3 associated with each hole. Bonding stand 17, furnished on an X-Y table (not illustrated), furnishes bonding stage 18 with an interior heater. Semiconductor element 4 is mounted on bonding stage 18.
Considering operation of a bonding apparatus so constructed, first a semiconductor element 4 is mounted on bonding stage 18, and bonding stand 17 is shifted in X-Y directions so that semiconductor element 4 is set in the proper position under hole 15 of guide plate 14. Carrier film 1 is transported in the direction of the arrow and is guided by guide plate 14 and guide rollers 16, 16a. Film transport stops after initial device hole 2 reaches a prescribed position over semiconductor 4. While being recognized by position recognition apparatus 13, bonding stand 17 and consequently semiconductor element 4 are shifted in X-Y directions. Referring to FIG. 8, electrodes 5 of semiconductor element 14 are positioned to match respective inner leads 3 projecting in device hole 2 of carrier film 1. The position of bonding stand 17, i.e. the position of semiconductor element 4, is stored in control apparatus (not illustrated). Bonding head 11 drops and presses heated bonding tool 12 against each inner lead 3a thereby fusing each lead to a respective electrode 5.
When the first bonding is completed, carrier film 1 is advanced one frame, the next device hole 2 stops in the prescribed position, bonding stand 17 with mounted semiconductor element 4 is positioned under carrier film 1 by a command from the control apparatus, and bonding is accomplished. Bonding is thereafter performed sequentially in the same manner.
In prior art methods of bonding leads to semiconductor elements, the objective is to bond after each inner lead 3a has been correctly positioned on electrodes 5 of semiconductor element 4 employing position recognition apparatus 13. When looking at the actual positional relationship between each inner lead 3a and electrodes 5 of semiconductor element 4, bonding is not always obtained as positioned before bonding. Slippage occurs primarily from limitations in the mechanical precision of bonding tool 12 and of position recognition apparatus 13. Bonding is accomplished with potential slippage in both the lateral (x) and horizontal (y) directions as shown in FIGS. 10 and 11 where broken lines depict position locations before bonding. Such slippage is rarely the same for each bonding cycle, there ordinarily being considerable differences in each cycle because of the mechanical precision of bonding tool 12 or position recognition apparatus 13.
The present invention resolves these and other problems by providing a bonding method capable of correctly positioning and securely joining the inner leads to the electrodes of semiconductor elements.